Photometer



(No Model.) 2 Sheets-Sheet 1.

J. L. FUELLING.

PHOTOMETER.

o. 589,649. Patented Sept. 7,1897.

UNITE Sra'rns ATENT much.

JOHN L. FUELLING, OFPEORIA, ILLINOIS.

PHOTOMETER.

SPECIFICATION forming part of Letters Fat en's No. 589,649, datedSeptember '7, 189 1.

Application filed October 26,1896. herial 1%. 610,188. No model.)

To (6U whom, if; may concern:

Be itknown that 1,.3' OHN L.FUELLING, a cili-' zen of the United States,residing at Peoria, in the county of Peoria and State of Illinois, haveinvented certain new and useful Improvements in Photometers; and I dohereby declare that the following is a full, clear, and exactdescription of the invention, which will enable others skilled in theart to which it appertains to make and use the same.

Myidea is to utilize the well-known susceptibility of the pupil of theeye to the action of light-rays, the pupil contracting or expandingaccording as the rays become stronger or less intense.

My device is adapted to measure the size of the pupil in any givenlight, such measurement being utilized for determining the time forexposing a sensitized platein photography.

One form of the device is shown in the accompanying drawings, in whichFigure 1 is a perspective view, Fig. 2 a side view, and Fig. 3 a planview. Fig. at is a similar view, the mirror-frame and the gage-framebeing folded down upon the main frame. Fig. 5 is a plan showing amodification of the indicator, and Fig. 6 is a vertical longitudinalsectional view thereof.

Referring to the various parts by letter, B designates a metal plate,which is preferably oblong in shape and is provided along its longitudin al edges with upturn ed flanges b.

A is an upright metal frame which is pivoted at its lower end betweenthe flanges of the plate 13 at the forward end thereof. This frame isadapted to fold down between the flanges Z), and carries the pupil-gage,which consists of two upright plates, one of which, E, is rigid, and theother, F, being movable to and from the rigid one to vary the size ofthe space I between them. The plate F may be adjusted by any suitablemeans, an ordinary set-screw I) being shown, said screw being threadedthrough the vertical side of the frame A and connected to the plate F.

The two plates E and F may be formed of any suitable material. As shownin the drawings, they are formed of transparent material, such as glass;but it may be desirable for some purposes to form them of opaquematerial.

l Atthe rear end of the frame or plate B is provided a frame A, similarin form to plate A, and this frame is also adapted to fold down betweenthe flange 1). this frame-that is, on the side facing the frame Aismounted a small magnifyinginirror II.

The size of the opening I between the plates E and F may be indicated byany suitable scale, and this scale may be carried by the frame A, asshown at G in Figs. 1 and a, or it may be secured to the plate B, asshown in Figs. 5 and 6. In this latter case an amplifier .I maybepivoted on the platcB and connected at its real-end to the movable plateF, its free end extending over an enlarged scale L. In this manner thevery delicate movement of the plate F will be readily noted and veryfine and accurate calculations may be made. The rear end of theamplifier is connected to the plate F by a pin M, which when the frame Ais in an upright position fits in a slot N in the rear end of theamplifier, as shown.

The manner of gaging the size of the pupil to determine the length ofthe exposure of the plate is as follows: The'frames A and A are placedin an upright position and the gage is held close to theeye, the inneredge of the stationary plate E being on a line with one edge of thepupil. The movable plate is then adjusted until its inner edge comes inline with the opposite edge of the pupil, the size of the pupil beingshown by the size of the opening between the plates, and this may beindicated by the scales G or L, as desired. The number ofgraduation-lines between the plates or between the end of the indicatorJ and zero on the scale L will indicate the length of the exposure.

It Will be observed that the operator sees the magnified image of hiseye in the mirror, which enables him to readily and with great accuracyadjust the gage-opening to the size of the pupil.

In using the device the photographer stands near his camera and looks atthe object, he wishes to photograph, and the light reflected from thatobject affects the pupils of his eyes. If the object be white, thepupils will contract, but if it be dark they will expand, and thisvariation in the size of the pupil de- 011 the inner side of.

termines the length of exposure. \Vhi1elooking at the object to bephotographed, the pnpil-gage is raised to one eye and the size of thepupil measured. In this manner the light which is to directly affect thesensitized plate is dealt with in operating the gage, and the lightreflected from objects immediately around the camera which will not beincluded in the picture do not directly affect the gage, as is the casewith other photometers. All objects to be included in the picture willbe Within the range of the eye and the pupil will be aifected by thelight reflected from them and an accurate determination of the length ofthe proper exposure will be obtained.

It will also be noted that there is no expense attached to the use of mydevice except, of course, the original cost, and is so small that it maybe carried about the person, or it may be attached to the camera.

It will also be noted that by giving a decimal scale or a scale which isso divided that every line is equal to a decimal part of a second orminute, one has only to determine the value of the same as compared tohis eye and lens to be able to make use of the scale readily withvarying intensities of light.

It will of course be readily understood that the device may be used formeasuring the intensities of lights by indicating their effect upon theeye, for measuring the effect of colors upon the eyein fact, in allcases Where it may be desirable to determine accurately the dilations ofthe pupil of the eye.

Having thus fully described my invention, what I claim, and desire tosecure by Letters Patent, is-

1. In a photometer, the combination, of a mirror, a pupil-gage, andmeans for supporting the mirror and the gage opposite each other,substantially as described.

2. The combination, in a photometer, of a magnifying-mirror, and apupil-gage, supported opposite the same, substantially as described.

In a photometer, the combination or a supporting-plate, a mirror carriedthereby, and a transparent pupil-gage, opposite said mirror,substantially as described.

4;. In a photometer, the combination, or a magnifying-mirror and atransparent pupilgage, and means for supporting them opposite eachother, substantially as described.

5. In a photometer, the combination, Of a mirror and a pupil-gageopposite the mirror. said gage consisting of two plates having avariable openingbetween them, substantially as described.

6. The combination, in a photometer, of a supporting-plate, amagnifying-mirror, and a pupil-gage, said pupil-gage consistingessentially of two plates and a graduated scaleplate, and means foradjusting one of the plates to and from the other plate substantially asdescribed.

7. The combination, of a main plate, a mirror-carrying frame pivoted atone end thereof. and adapted to fold down thereon, and a pupil-gagepivot-ed at the other end of the main plate and also adapted to folddown thereon, substantially as described.

8. The combination, in a photometer, of a supporting-plate, a mirrorcarried thereby. a pn pil-gage consisting of two plates, means foradjusting one of said plates to and from the other plate, an amplifierconnected to said movable plate, and a scale-plate, substantially asdescribed.

In testimony whereof I affix my signature in presence of two witnesses.

JNO. L. FUELLING.

Witnesses JOHN .B. SAMUEL, LILLIAN E. BALZER.

